1. Field of the Invention
In an optical system an optical element may need to be rotated about an axis and require one or two other axes for alignment. The present invention is a device and method for providing such alignment by gimbaling the axis of rotation of the optical element.
2. Description of the Prior Art
Typically in the prior art, an optical element required to rotate about one axis and be adjustable for alignment purposes about the other one or two axes is held in a mount which is coupled directly to the rotational axis. The optical element is aligned about the other one or two axes relative to this mount. That is, in the prior art the axis of rotation is fixed and the optical element is moved by its mount relative to the axis of rotation.
This prior art approach is satisfactory for some systems. However, in other systems it is important for the purposes of the system of which the Optical element is a component that the optical element be rotated very quickly and accurately. In these systems the prior art is deficient because the mass of the mounting substantially increases the mass moment of inertia of the optical element, and so makes fast and accurate rotation difficult. FIG. 1 illustrates a typical prior art mount 20 for a diffraction grating 24, having diffraction surface 26. The axis of rotation of grating 24 is A.sub.R. Two screws 28A, 28B (only one of which 28A is fully shown) provide adjustment of grating 24 about one axis. A screw 30 provides adjustment about a second axis.
Other commercially available prior art mounts used for non-rotating optical elements (not shown) are gimbal mounts for optical elements which allow adjustment of the optical plane of the optical element about two axes independently by fine pitch micrometer screws. However, these mounts do not provide any axis of rotation for the optical element. That is to say, these commercially available mounts are adjustable but not rotatable.